firewire: ohci: wait for local CSR lock access to finish

Add a loop to wait for the controller to finish a locally-initiated CSR
lock operation.  Google shows some occurrences of the "swap not done
yet" message which might indicate that some OHCI controllers are not
fast enough to do the lock/swap in the time needed for one PCI access.

This also correctly handles the case where the lock operation did not
finish, instead of silently returning an uninitialized value.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 82fb2e7e99ef337affedb52a1c7d715aa8894e93..6e95f8fb56db7eba68a55eb73e83989a4f7d3dd0 100644 (file)
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -1158,7 +1158,7 @@ static void handle_local_lock(struct fw_ohci *ohci,
                              struct fw_packet *packet, u32 csr)
 {
        struct fw_packet response;
-       int tcode, length, ext_tcode, sel;
+       int tcode, length, ext_tcode, sel, try;
        __be32 *payload, lock_old;
        u32 lock_arg, lock_data;
 
@@ -1185,13 +1185,19 @@ static void handle_local_lock(struct fw_ohci *ohci,
        reg_write(ohci, OHCI1394_CSRCompareData, lock_arg);
        reg_write(ohci, OHCI1394_CSRControl, sel);
 
-       if (reg_read(ohci, OHCI1394_CSRControl) & 0x80000000)
-               lock_old = cpu_to_be32(reg_read(ohci, OHCI1394_CSRData));
-       else
-               fw_notify("swap not done yet\n");
+       for (try = 0; try < 20; try++)
+               if (reg_read(ohci, OHCI1394_CSRControl) & 0x80000000) {
+                       lock_old = cpu_to_be32(reg_read(ohci,
+                                                       OHCI1394_CSRData));
+                       fw_fill_response(&response, packet->header,
+                                        RCODE_COMPLETE,
+                                        &lock_old, sizeof(lock_old));
+                       goto out;
+               }
+
+       fw_error("swap not done (CSR lock timeout)\n");
+       fw_fill_response(&response, packet->header, RCODE_BUSY, NULL, 0);
 
-       fw_fill_response(&response, packet->header,
-                        RCODE_COMPLETE, &lock_old, sizeof(lock_old));
  out:
        fw_core_handle_response(&ohci->card, &response);
 }